Preheat oven to 350 degrees. Line a baking sheet with foil. For Mornay sauce, in a saucepan, combine broth and butter over medium heat; whisk in Alfredo sauce mix. Bring to a boil, stirring constantly. Reduce heat; simmer for 2 minutes. Add 1 1/4 cups of the Swiss cheese, stirring just until melted. Remove from heat. Divide sliced turkey among split English muffins. Top with Canadian bacon, tomato, and asparagus; place on a baking sheet. Spoon the Mornay sauce over; top with remaining 1/2 cup of Swiss cheese. Bake in preheated oven about 20 minutes or until heated through and cheese is bubbling and just starting to brown.